1. Field of the Invention
This invention relates to an artificial middle ear and ear canal prosthesis.
2. Description of the Prior Art
The human middle ear system, which is responsible for the transmission of sound vibrations to the inner ear is describable as follows: "A bony canal ends in a bony annulus or ring. A drum membrane is fixed in the ring. The middle ear bone chain is connected via the hammer to the drum membrane that makes contact with the inner ear via the anvil and stirrup. The contact of the stirrup with the oval window provides for the transmission of sound vibration in the inner ear. The efficient transmission of sound depends upon the viability of the drum membrane and the effective contact of middle ear chain with the oval window."
The efficient transmission of sound can be destroyed or substantially reduced by chronic otitis media. This disease can destroy part or all of the total middle ear system. It may even destroy parts of the bony external ear canal. The inner ear, the facial nerve and the brain may also run the risk of being attacked.
In view of the foregoing it is desirable for a surgeon to remove the entire diseased area in order to avoid reoccurence. Such drastic surgery will frequently result in a substantial hole in the mastoid.
Attempts to reconstruct the middle ear system were begun approximately 20 years ago. Since then many systems have been developed in order to restore sound conduction. Autologous materials were originally used for reconstruction purposes. Unfortunately, up until the present, a total reconstruction has been impossible.
Towards the end of the late 1960's inert materials such as Teflon and polyethylene were employed as prosthesis in order to restore the middle ear bony chain. These prosthesis were placed between the preserved portions of the patient's middle ear. Generally the initial results were satisfactory but eventually the prosthesis were extruded by the middle ear. Teflon is still the preferred material as the substitute for the stirrup.
Subsequently a method was developed which eradicated the disease and kept intact the bony canal and the bony annulus. This technique made it possible to do implantations of homologous middle ears. These implantations consisted of a drum membrane, hanmer, anvil and stirrup. That was the first time that the induction system of the middle ear was restored in toto.
Another problem that arose was the desirability of preserving an intact bony ear canal and bony annulus. Eventually, the reconstruction of the middle ear was made secondary to the definite sanitation of the chronic otitis media. Debate still continues about the recurrence of chronic otitis media. The results obtained with regard to sound conduction by a homologous middle ear structure are varying. In the development of otology the use of biocompatible materials was not begun until 1970. At that time an ossiclar replacement prosthesis was developed by Charles A Hamsy in cooperation with John Shea. A description of a device can be found in U.S. Pat. No. 3,909,852. The prosthesis described in that patent was developed to replace the bony middle ear chain. Fixation of the device was made possible by the use of a micropourous implant material which has the characteristics of promoting living tissue. The prosthesis described in U.S. Pat. No. 3,909,852 is characterized by only a single columella which is fixed at the ends thereof to the ear drum and oval window. The use of the prosthesis is predicated on the existence of a normal ear drum having an intact canal wall and a totally eradicated middle ear cleft.